This application claims the priority of Japanese Utility Model Application No. 95269/1991, filed Nov. 20, 1991.
FIG. 4 exhibits a prior device for binding post members: a coupling of a handle post and second coupling of a handle bar. In FIG. 4, a handle post coupling 1 consists of a handle post 12 and a handle clamp 1a. The handle clamp 1a has an arm 13, a binding cylinder 11 for a handle bar A and a binding cylinder 10 for the handle post 12. A conventional coupling is now explained by describing the handle post coupling 1. The binding cylinder 10 of the clamp 1a has tightening ears 16, 16' which face each other with a small clearance 17. The tightening ears 16, 16' are perforated by holes extending a direction normal thereto. The handle post 12 is inserted into an inner hole of the binding cylinder 10. A bolt 14 penetrates the holes in the tightening ears 16, 16'. A nut 15 is engaged with an end of the bolt 14. Then, the nut 15 is tightened. The clearance 17 decreases. As a result, the inner surface of the binding cylinder 10 is strongly urged against the handle post 12. Therefore, the handle clamp 1a is tightly bound to the handle post 12 by the bolt 14 and the nut 15.
However, this binding structure suffers a drawback that the tightening force is gradually weakened by a loosening of the nut 15 from the bolt 14. In the conventional coupling, the direction of the tightening force produced by the bolt and nut, is the same as the direction of the axis of the bolt. Vibration accompanying the riding of the bicycle is likely to generate a force to loosen the bolt and nut. Since the force for loosening acts along a line parallel to the bolt, the bolt and nut are apt to loosen from each other. Coincidence of the direction of the bolt and the force of vibration is likely to result in a loosening of the hold of the bolt and nut to the cylinder 10.
The above describes an example of the loosening of the coupling of the handle post. A second coupling, of a seat post to a frame, has the same drawback. The loosening of couplings of post members must be prevented to obtain a stable structure of a bicycle.
A purpose of this invention is to provide a binding structure which can hold down the decrease of binding force brought about by loosening of a bolt and nut. Another purpose of the invention is to provide a binding structure which keeps a good hold between post members and other parts despite long term use of a bicycle.